The present invention relates to a sheet post-processing device and an image processing apparatus. More particularly, the present invention relates to a sheet post-processing device for performing a folding operation and a saddle stitching operation on a sheet stack discharged from an image forming apparatus and an image forming apparatus having such a sheet post-processing device.
Conventionally, an image forming apparatus such as a copier, printer, facsimile or a combination thereof, forms an image onto a sheet, and is equipped with a sheet post-processing device mountable to the image forming apparatus. A certain type of sheet feeding apparatus folds discharged sheets to form a finished booklet with the edges of the sheets neatly aligned (or perform a binding process).
Such a sheet feeding apparatus performs the folding operation in which, for example, a folding blade pushes the sheet stack and rotating bodies such as folding rollers nip and fold the sheet stack.
However, in the conventional sheet feeding apparatus, when the folding blade pushes the sheet stack into a nipping point of the folding rollers, it is difficult to convey the sheet stack between the folding rollers, resulting in a folding jam, and the sheet stack is not folded.
Such a folding jam occurs when the folding rollers convey the sheet stack with an insufficient force. Also, the nipping point of the folding rollers for folding the sheet stack is fixed at a constant position. Therefore, when the folding blade does not push the sheet stack into the nipping point of the folding rollers with a sufficient force, the sheet stack tends to stay at a position away from the folding rollers.
Accordingly, it is an object of the present invention to provide a sheet post-processing apparatus for securely folding the sheet stack.
Further objects and advantages of the invention will be apparent from the following description of the invention.